The present invention relates to a rangefinder, e.g. for an electronic pen, and, more particularly, to a rangefinder and recorder, e.g. for an electronic pen, that records the user's handwriting continuously as the user moves from one page to the next.
FIG. 1 is a combined plan view and schematic block diagram of a combined rangefinder and recorder 10 for an electronic pen. On a lateral surface 14 of a housing 12 of rangefinder 10 are two spaced-apart ultrasound receivers 16 and an infrared receiver 18 that are operationally connected to rangefinding circuitry 20. Ultrasound receivers 16, infrared receiver 18 and rangefinding circuitry 20 operate in a manner that is taught e.g. in U.S. Pat. No. 6,151,014 to track the movement of an electronic pen (not shown) in the plane of FIG. 1. The pen periodically emits simultaneous omnidirectional infrared and ultrasound pulses. The infrared pulses are received by infrared receiver 18. The ultrasound pulses are received by ultrasound receivers 16. The time delays between the receptions of the individual infrared pulses and the associated individual ultrasound pulses, and the mutual time delays between the receptions of the individual ultrasound pulses at the two ultrasound receivers 16, are measured by rangefinding circuitry 20 and are used by rangefinding circuitry 20 to locate the pen relative to rangefinder 10 by triangulation. These measurements of the instantaneous location of the pen are sent by rangefinding circuitry 20 to recording/playback circuitry 22 that records the measurements in a flash memory 24 as a record of the handwriting of the user of the pen. Subsequent to the recording, the user may download the record of his/her handwriting from memory 24 via recording/playback circuitry 22 and a USB port 26. Power for circuitry 20 and 22 and for flash memory 24 is provided by a battery 28.
U.S. Pat. No. 6,151,014 is incorporated by reference for all purposes as if fully set forth herein.
In the system composed of rangefinder 10 and the electronic pen, the infrared pulses provide timing signals for timing the arrivals of the ultrasound pulses. In an alternate embodiment (not shown) the electronic pen is connected to rangefinder 10 by a waveguide such as a fiber optic cable and the infrared pulses are transmitted by the pen to the rangefinder via the waveguide. The waveguide is optically coupled to infrared receiver 18 and to the infrared transmitter of the pen. In yet another embodiment (also not shown), the electronic pen emits pulses of electrical voltage as timing pulses. The pulses of electrical voltage are conveyed to rangefinder 10 via flexible electrical conductors; and, instead of infrared receiver 18, rangefinder 10 is equipped with a detector of such pulses.
Rangefinder 10 may be secured e.g. by a clip to a pad of paper to allow the user to record his/her handwriting on the pad. One capability that is lacking in rangefinder 10 is the ability to automatically mark transitions from one sheet of paper to another. Such a capability, as well as others, is provided by the present invention.